Global animal, bird and fish populations have plummeted more than two-thirds in less than 50 years due to rampant over-consumption, experts said Thursday. The WWF's biennial Living Planet Index, which tracks more than 4,000 species of vertebrates, warned that increasing deforestation and agricultural expansion were the key drivers behind a 68 percent average decline in populations between 1970 and 2016. pg/klm/bp